1. Field of the Invention
This invention relates to electronic microminiature modules and, more particularly, to a novel modular package having a sandwich construction and heat sink apparatus which provides reliable mechanical and electrical securement between the active elements of the module and conductive terminals carried on the module.
2. Brief Description of the Prior Art
As the usefulness of electronic equipment has expanded with the increase in technological improvement and with the widening demand, both militarily and commercially for equipment capable of handling vast quantities of information at increased rates of speed, the need for high density electronic packaging has become of increasing importance. A concomitant of this trend is the need for circuit protection and miniaturization which, while providing the requisite component density, maintains both system reliability and serviceability. Under the thrust of this expanding use, it has become an economic necessity to provide a circuit component construction which is of reduced density and which includes interconnecting means for coupling into the electronic equipment which both minimizes the possibility of error in field maintenance procedures and reduces overall system complexity.
With increasing component packaging density, the reliability of circuit interconnections and heat dissipation has become of paramount significance. Particularly, this is true with respect to the design, construction and interconnection of circuit components and assemblages which carry out the basic work function of the electronic equipment. Conventionally, the electrical circuit network generally comprises a plurality of logic circuits such as "gates" and "flip-flops" interconnected to form an electronic complex designed to carry out the various arithmetical and logical functions for which the equipment is programmed.
These basic circuits lend themselves to compact arrangement on printed circuit boards or cards or on substrates in thin film semiconductor form wherein discrete components are employed. The substrate or printed circuit board generally carries strips of conductive material disposed in a predetermined pattern terminating in conductive pads arranged along one or more sides of the substrate or board which are employed for external connection purposes so as to permit interconnection of the circuit carried on the substrate or board with other associated circuits mounted on the electronic equipment.
One means for making mechanical and electrical contact with the conductive pads on a substrate or circuit board comprises the use of pins or leads that are attached to the respective conductive pads at one end, and having their opposite ends exposed exteriorly of the packaging module for external connection with other equipment such as a larger printed circuit board. Normally, the pins or leads are attached to the conductive pads by means of hand soldering, welding or bonding techniques, and the substrates, including the pins or leads are then mounted in a suitable case. Next, a suitable potting compound is used to encapsulate both the active and passive devices carried on the substrate as well as the pins and lead connections with the conductive pads. In this fashion, a conventional modular package is produced.
However, problems and difficulties have been encountered when fabricating and using such a modular package, which stem largely from the fact that many of the fabricating procedures require hand or manual operations which are time consuming, and such fabrication procedures are susceptible to inaccuracies and faulty connections caused by human error. Also, the substrate material, potting compound, and the package casing material generally have different coefficients of expansion, so that when the module is subjected to temperature cycling during the operation of the unit within its given environment, the securement between the pins or leads with the respective conductive pads have a tendency to shear and interrupt circuit continuity. Furthermore, the size of the component is relatively large when assembled as compared to the active or passive elements comprising portions of the total package.
Therefore, a long standing need has existed to provide a microminiature electronic package which incorporates a heat sink for heat dissipation purposes and an electronic package of miniature construction which lends itself to high density assembly on a circuit board or substrate.